OBJECTIVES: To evaluate test-retest reproducibility and the validity of a physical activity questionnaire for adolescents (adapted from Self-Administered Physical Activity Checklist). METHODS: The test-retest reproducibility analysis was completed by 239 adolescents (average age 16 years, SD = 1.2; 56.4% female), and the validity analysis by 70 adolescents (average age 15.7 years, SD = 1.2; 55.7% female). All adolescents were high school students in João Pessoa, PB, in Northeastern Brazil, in 2009. The test-retest reproducibility was determined by repeated evaluations with one week interval between them. Validity of the physical activity questionnaire was assessed by comparing the results of the questionnaire with those of four 24-hour recalls (reference method). RESULTS: The test-retest reproducibility was high (intraclass correlation coefficient: ICC = 0.88; 95%CI: 0.84 - 0.91), and the agreement was moderate for physical activity classified in two groups (< 300min/week vs. > 300min/week; kappa coefficient: k = 0.52). Spearman correlation coefficient comparing the questionnaire data with those of four 24-hour recalls (reference method) was moderate (rho = 0.62; p < 0001). The agreement between these measures (questionnaire and 24-hours recalls) for physical activity classified in two groups was moderate (k = 0.59). CONCLUSIONS: The physical activity questionnaire showed high reproducibility, and moderate validity, and therefore, its use is recommended for assessing adolescents' physical activity level.